The invention relates to a method for reducing uncontrolled combustions in an internal combustion engine, which occur independently of the ignition by a spark plug, wherein the uncontrolled combustions in the in the internal combustion engine are detected and a device is provided for carrying out the method.
In a gasoline engine, a combustion of the fuel/air mixture supplied leads to the vehicle being set into the driving operation, respectively the driving operation being maintained. The combustion of the fuel/air mixture is thereby initiated by the spark of a spark plug. While the flame front spreads in the combustion chamber, self-ignitions occur as a result of high pressures and temperatures. The combustion, which then occurs abruptly, causes a precipitous increase in pressure which in turn produces a pressure wave. Said wave spreads and impacts the walls bounding the combustion chamber, whereat the high frequency vibrations are converted into structure-borne noise. In controlling the gasoline engine, these vibrations are detected by knock sensors (structure-borne sound sensors) and are taken into account by a knock control system in order to prevent damage to the engine. In so doing, said gasoline engine is always operated in an optimally efficient manner at the knock threshold, whereby damage to said engine as a result of knocking is avoided.
Besides the knocking combustion just described, self-ignitions, however, also occur, which are caused by hot spots in the combustion chamber, oil droplets or hot residual gas zones in the fuel/air mixture. Such self-ignitions can also occur as pre-ignitions prior to the ignition spark occurring or as post-ignitions after said ignition spark occurs. The self-ignitions are characterized by compression pressures with high pressure amplitudes and/or gradients, which can very quickly lead to engine damage.